70 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 20, 



who has visited the districts of Alton, Cheadle, and Trentham, 

 or climbed the escarpments of the Hawkestone, Peckforton, and 

 Runcorn ranges, can deny to the New Red Sandstone an amount 

 of scenic power almost comparable with that of the Oolites of 

 Gloucestershire . 



3. Lias. — A. Lower Lias. — We have not, unfortunately, the same 

 facilities for making comparisons of the development of the Lower 

 Lias in the Western and Eastern Districts. With the exception of 

 the outlier at Prees in Shropshire, and a newly discovered area of 

 the same formation near Carlisle*, we have no districts of com- 

 parison ; and, as these do not present us with the whole ascending 

 series, they are useless for our purpose. I therefore propose to 

 treat this formation by analogy. It must be allowed that there 

 is a close connexion between the Lower, Middle, and Upper 

 Lias formations. As far as we can judge, the strata are strictly 

 conformable. There are no breaks greater than between different 

 subdivisions of the Inferior Oolite. There is a generic community 

 of the fauna ; and the mineral characters of the series are re- 

 peated at intervals throughout. We are, therefore, justified in 

 supposing that all the Liassic formations of central England 

 have had their origin from the same sources and under similar 

 physical conditions, and are therefore equally subject to attenua- 

 tion when receding from those sources. If, therefore, it can be 

 shown that there is a tendency on the part of the Marlstone and 

 Upper Lias to thin away towards the south-east, and that this at- 

 tenuation takes place within the range of actual observation, there 

 will be strong grounds for inferring a similar propensity on the part 

 of the Lower Lias ; at least, it is upon these grounds that I base 

 the analogy. When we come to consider, in a subsequent part of 

 this paper, how strong are the reasons for believing that all these 

 formations have been derived from regions lying to the north- 

 west of the British Islands, the analogy will be found to gain 

 additional force. 



B. Marlstone. — Let us now trace the Marlstone along its S.E. 

 extension towards Oxford. At Bredon Hill (see Plate IV. fig. 1), 

 a large outlier near the confluence of the Avon and Severn in North 

 Gloucestershire, the Marlstone attains a thickness of 250 feet ; 

 probably the greatest known in this part of England. On the flanks 

 of Ebrington Hill, the extreme northern termination of the Cottes- 

 wold Range, the thickness, as computed by Mr. Howell, is 150 

 feett ; at Leckhampton Hill, near Cheltenham, the thickness is 

 115 feetj, by accurate measurement, which is the average develop- 

 ment of the formation along the whole of the Cotteswold Hills. 



of the surface, by one who possesses a perfect knowledge of the succession of the 

 beds. These faults admirably bear out the principles laid down by Mr. Hopkins 

 of Cambridge, followed by Mr. Jukes and Professor Haughton. 



* Recently communicated to the Manchester Geological Society by Mr. 

 Binney. See also Quart. Journ. Geol. Soc. vol. sv. p. 549. 



t " Geology of the Country around Cheltenham," Mem. Geol. Survey, 1857, 

 p. 19. J Ibid, plate 2. 



